[Python] ##[error]Error: Error: Failed to deploy web package to App Service. Conflict (CODE:...

I've been trying to deploy my FastAPI application on Azure DevOps for the past two days. It was working perfectly before, but now it's not working even though I haven't made any changes to the pipeline.

My Pipeline is:

trigger:
- main

variables:
azureServiceConnectionId: service_connectionID
webAppName: appname
vmImageName: 'image'
environmentName: 'env'
projectRoot: $(System.DefaultWorkingDirectory)
pythonVersion: '3.11'

stages:
- stage: Build
displayName: Build stage
jobs:
- job: BuildJob
pool:
vmImage: $(vmImageName)
steps:
# Set up Python environment
- task: UsePythonVersion@0
inputs:
versionSpec: '$(pythonVersion)'
displayName: 'Use Python $(pythonVersion)'

# Install dependencies
- script: |
python -m venv antenv
source antenv/bin/activate
python -m pip install --upgrade pip
pip install setuptools wheel
pip install -r requirements.txt
workingDirectory: $(projectRoot)
displayName: 'Install requirements'

# Create deployment package
- task: ArchiveFiles@2
displayName: 'Archive files'
inputs:
rootFolderOrFile: '$(projectRoot)'
includeRootFolder: false
archiveType: zip
archiveFile: $(Build.ArtifactStagingDirectory)/$(Build.BuildId).zip
replaceExistingArchive: true

# Publish build artifacts
- task: PublishBuildArtifacts@1
inputs:
PathtoPublish: '$(Build.ArtifactStagingDirectory)'
ArtifactName: 'drop'
publishLocation: 'Container'

- stage: Deploy
displayName: 'Deploy Web App'
dependsOn: Build
condition: succeeded()
jobs:
- deployment: DeploymentJob
environment: $(environmentName)
pool:
vmImage: $(vmImageName)
strategy:
runOnce:
deploy:
steps:
# Deploy the web app
- task: AzureWebApp@1
displayName: 'Deploy Azure Web App'
inputs:
azureSubscription: $(azureServiceConnectionId)
appType: 'webAppLinux'
appName: $(webAppName)
package: '$(Pipeline.Workspace)/drop/$(Build.BuildId).zip'
runtimeStack: 'PYTHON|3.11'
startUpCommand: 'startup.txt'
deploymentMethod: 'auto'


My startup command is :

gunicorn -w 4 -k uvicorn.workers.UvicornWorker --timeout 600 -b 0.0.0.0:8000 app:app


and its giving me error as

##[error]Failed to deploy web package to App Service.

##[warning]Can't find loc string for key: KuduStackTraceURL

##[error]KuduStackTraceURL https://ai-commission-dsbfcbduhcb6gtfz.scm.eastus2-01.azurewebsites.net/api/vfs/LogFiles/kudu/trace

##[error]Error: Error: Failed to deploy web package to App Service. Conflict (CODE: 409)

##[warning]Error: Failed to update deployment history. Error: Bad Request (CODE: 400)

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